The End of IPv4 and the Amateur 44/8 amprnet

Image via WikipediaI wrote about amprnet (ampr.org) a while back - here.  It's a relatively unknown fact that ham radio has its very own Class A IP network -- 44.0.0.0/8.  This is quite a huge chunk of Internet IP v. 4 address space -- 16 million addresses, give or take.  As best I can determine, it was established in 1987 to support future TCP/IP networks that might be implemented either on radio links or as some combination of radio and alternative commercial or other links.  (The latter makes a lot of sense now, given the widespread availability of consumer Internet connections.)  The allocation is best documented in this ARIN WHOIS link.  I have not been able to find on-line documentation or other material relating to amprnet, beyond a number of blog and email postings.  (I'd be happy to get pointers!)

This whole subject came up once again for me, when I was reading how ARIN is trying to "capture" (contractually speaking) the legacy owners of IPv4 address space.  These are people, presumably including amprnet, who received their allocations well before the current Internet bureaucracy was established.  An interesting look at the issues is available in ComputerWorld.  (Thanks slashdot!)

The amprnet allocation usage must be tiny in percentage terms, and hard to justify in a world of address scarcity.   Standalone radio networks based on TCP/IP (if there really are any!) are likely based on VHF if not 2.4 GHz (HSMM), and they are fundamentally local or regional and are not likely to be routable from the Internet.   They could probably equally well use a network address like 10.0.0.0/8.

In recent years, various other network-based amateur systems have developed, including EchoLink, IRLP, D-Star, winLink, etc.  These make effective use of Internet links, but have no particular need for the amprnet addresses.

I don't want to argue the pros and cons so much as to point to the odd situation of our hobby holding such a valuable resource, with no visible institutional support. 

What are the chances to get a little more RF spectrum, if we hand back the IP addresses?

U-verse Downs & Ups

Image via WikipediaThe AT&T U-verse saga continues.  I was sad to find that, after my initial tests that showed I could run 80 M CW at 800 W, my latest round of tests showed really bad sensitivity.  I couldn't run over 20 or 30 W without causing the U-verse Residential Gateway (RG) to lose sync.  (That can mean a 1- or 2-minute TV and phone outage.)

After a bit of probing, it became clear that the RFI was entering on the internal home phone wiring.  Disconnecting it from the RG quieted the problem, but alas we are now very dependent on the U-verse VOIP service.  Disconnection is not an option, normally.  (Cell coverage is poor here - a story for another day.)

The AT&T installer had not fully appreciated my phone entrance system, which uses a special DSL surge suppressor that is bolted onto my Single-Point Ground system.  He ran his CAT5 cable from the wall plate straight into the RG. (That's OK for RFI, but not great for lightning surges.)  The house phones were fed via a circuitous route passing (backwards!) through the surge supressor, and generally making a nice RF pickup loop.

This afternoon, I pulled out half my station (the heavy part!) so I could get access, and rewired the phone system, adding ferrite chokes, etc.  Result: no trouble now with 800 W at 3600 kHz.  I'll do more tests later, when the contest goes away.

U-verse RFI tip:  You can use the ubiquitous DSL telephone line filters as an RFI choke.  These are transparent to telephone audio, but block the DSL frequencies.  (It's not clear whether they are effective at up to ~8 MHz that VDSL = U-verse uses, but it seems likely they are.)

More complete info will be at http://aa6e.net/wiki/RF_Compatibility.

Music from Outer Space - Design Tools

Design in your browser. An integrated web-based schematic capture and breadboard support system provided by Music from Outer Space.  It's oriented toward audio, not RF, but it's a cool site for simple designs.


(tnx jameco.com)

VAIO inverter surgery

 

My Sony VAIO (VGN-FS710/W) gave up the ghost last month. The screen went dark, and it emitted some screechy noises.  I figured what a hardware service call would likely cost, and I decided I quickly needed a new laptop to support my work at ARRL and other things. So I sprang for a new inexpensive Toshiba (Satellite L6460), which did not cost much more than that hypothetical service call.

Now, after my computing situation has stabilized, I had a chance to open up the VAIO to see what could be done.  There were some helpful disassembly hints on the Internet, and they were essential to avoid breaking things.  The culprit almost leaped out at me.  It's the tiny inverter card (above) that makes high voltage to run the fluorescent LCD back light.  The Internet (again) seems to be saying this is a frequent source of problems.  The HV rectifier was charred and broken, so obviously this was the problem.  It's a $50 part, and I hope replacing it will solve the problem.

I suppose there's a moral here.  I could have saved money, but incurred opportunity cost and risk, if I simply repaired the VAIO.  I'm happy to have a new, more powerful laptop. Still, the VAIO is handy because it has some critical features (like Firewire) that make it very useful for some of my work.

Update (11/12/2010): Thanks to lcdparts.net, I have a new inverter, and the VAIO is back in operation!

Spectrum and Band Occupancy

Dan, KB6NU, has some good reasons to worry about 300-3000 MHz competition for amateur bands.
Image via Wikipedia
Right on.  At least frequencies below 300 MHz are under less pressure, which is a relief to us HF & 2M troglodytes.  Still, vigilance is required.  Support ARRL.

There is a problem with the VHF and higher bands that doesn't get a lot of attention.  Amateurs are not very good at utilization.  The bands are almost always completely empty, and this makes them targets for commercial use.  Around here in CT, the 2M repeater segments are mostly allocated and unavailable for new applications, but they are still unused most of the time.

Image via WikipediaBy contrast look at 14.070 - 14.073 kHz. I can often copy dozens of PSK31 QSOs in progress there in 3 kHz of spectrum.  Also look at the cell/CDMA bands that support 100s of "QSOs" in a few MHz all the time.  Hams do need to pay more attention to band occupancy.

BARTG RTTY result

My first ham contest in a long time was the BARTG RTTY affair in March.  I just checked up on the results and found where I fit into the grand scheme of things.  I don't feel bad about it, though there's a lot of room for improvement! (These are the 328 "non-expert" full contest entries.)

More U-verse work

I did some more testing on U-verse vs HF QRO operation today.  The main results are reported at http://aa6e.net/wiki/Uverse, which is going to be where the data from this work is accumulated.  We only give the late breaking news here.

As expected, winding the incoming DSL line on a ferrite core (8 turns, type 77) has helped a fair bit -- allowing a doubling of amplifier power on a good range of frequencies.  We also see that the U-verse DSL does not show any problems for QRO at 20 meters and up.  80 and 40 (and 160) are going the be the troublesome bands.

But we have more countermeasures we can try.  That will be for another day.

I also have trouble with my carbon monoxide detector going off.  (It's very loud!)  And pickup in my computer loudspeakers is annoying on 40 M.  All this will yield to filtering.

Uverse vs 80 meters

So, we've finally got to the point of some stability with Uverse in the house for TV, Internet, and telephone service.  That is, without doing much ham radio.

I discovered a nice tool, U-Verse Realtime, which lets you show many parameters of your Uverse operation. It's free software for Windows machines, and it seems to work in my virtual Windows XP machine.  (VMware under Ubuntu Linux.)

The first bit of science is to measure my "bitloading".  That shows what parts of the frequency spectrum are being used for the underlying DSL connection.  The results:

The chart shows that frequencies between about 100 kHz and 3.7 MHz are used for download (yellow), while 3.7 - 5.0 MHz are used for upload (green).  There is a small higher region, about 5.3 - 5.5 MHz also allocated to download.

The increasing line attenuation with frequency is apparent.  (At least, if you believe that "bitload" has something to do with signal power.  I don't really know that.)  The electrically measured line length from the Uverse node is 2554 feet, which puts me in the lowest of 3 service tiers.

OK, second science test.  The active DSL spectrum includes the 80 and 160 M ham bands.  What's the interference potential?  This is not a simple question.  The interference from Uverse's DSL connection might not be much of a problem.  Why?  The received signal is going to be weak (indicated line attenuation is 21.6 dB.) The locally stronger transmitted signal, 3.7 - 5.0 MHz, is mostly outside the 80 M band, although there could be problems between 3.7 and 4.0 MHz, in the SSB band.  Fortunately (?), the 80 M band is naturally so noisy that the interference might not be noticeable.

The thing to worry about, I think, is interference to Uverse service.  I ran a very short test at ~3536 kHz CW.  I was downloading a large file over the Internet and listening to an HDTV program in the other room.  Transmitting with ~90 W output caused no apparent problems.  Transmitting at ~850 W killed the DSL connection pretty quickly.  Download stopped, and the TV image froze. It took about 70 seconds to reacquire the signal after transmission stopped.  (At least nothing was destroyed!)

This is all very preliminary.  We will need to improve the wiring and experiment with ferrite chokes -- probably on the incoming DSL connection.  There is no guarantee that kilowatt 80/160 M operation will ever work, but it might...